Struts are devices which provide mechanical assistance when raising, lowering, moving, and holding objects. Struts are elongated devices having a hydraulic or pneumatic cylinder and a rod which slides within the cylinder. The rod is generally fixed to a piston or other sealing device within the cylinder, which drives against a dampening medium, such as a gas or oil. The dampening medium is contained within the cylinder by a seal; generally, the seal between the cylinder and the rod is a gasket or O-ring.
Often, the seal between the rod and cylinder will wear out, causing the gas or oil in the cylinder to slowly leak out. When this happens, the strut becomes less effective at providing mechanical assistance. The strut will raise the object slower, or not at all, or will fail to keep an object elevated, or will lower an object too quickly. This problem is exaggerated when the operating temperature of the strut is low, because a drop in temperature will cause a drop in the pressure inside the cylinder on which the strut relies to operate properly. The strut eventually ceases to operate, and some other device must replace the strut.
As an example, struts are used in the automotive industry, in one instance, to hold up hoods, hatches, and liftgates of automobiles. A hood strut will hold the hood of an automobile open when a user is under the hood inspecting the engine compartment. When the hood is up, the strut is extended and generally keeps the hood open. Hoods can be quite heavy, and so a strut required to keep the hood open must both be strong and have good seals. As the seals begin to fail with time, the strut will become less effective at opening the hood and keeping the hood open. A user may have to lift the hood with more force, may have to hold the hood up with his arm, or eventually, may have to prop the hood open with another object, such as a pole, a broom stick, or the like. This poses a danger; should the propping device come loose, the hood could come crashing down, possibly on the user. An improved device for holding a strut in an extended position is needed.